3-Pyridinecarboxaldehyde → 3-(Cyclopentylidenemethyl)pyridine

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A suspension of cyclopentyltriphenylphosphonium bromide (226 g, 0.55 mol) in anhydrous tetrahydrofuran (1000 ml) at 2° C. was treated with vigorous stirring under an atmosphere of argon, with potassium t-butoxide (61.7 g, 0.55 mol). The dark red mixture was stirred at 5° C. for 80 minutes and then treated with pyridine-3-carbaldehyde (58.9 g, 0.55 mol) during a period of 20 minutes. The reaction mixture was stirred at 0° C. for 2 hours and then at 20° C. for 18 hours. The tetrahydrofuran was removed in vacuo (30° C.; 14 mmHg) and the residue extracted with pentane (2×500 ml). After treatment with decolorizing charcoal (5 g) the mixture was filtered through a plug of flash silica gel (Merck 70-230 mesh (13 cm×2 cm diameter). The filtrate was concentrated in vacuo (30° C., 14 mmHg, then 20° C.; 0.01 mmHg) to afford 3-cyclopentylidenemethylpyridine (54 g, 0.34 mol,) as an oil which was used without further purification. N.M.R. (CDCl3) 1.6-1.95 (m, 4H); 2.4-2.65 (m, 4H); 6.26-6.34 (m, 1H); 7.16-7.25 (ddd, 1H); 7.56-7.65 (ddd, 1H); 8.52-8.52 (d, 1H).

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